The present invention relates generally to a gate and a seal for the gate about the outlet of a material storage container and particularly relates to a gate seal for selectively opening and closing the outlet of an asphalt storage silo.
Storage silos are frequently used for storing various types of materials. Typically, such silos have conveyors for conveying the material from ground level to adjacent the top of the silo and depositing the material in the silo. An outlet is disposed adjacent the bottom of the silo and which outlet is typically situated above a drive-through material transfer station. Thus, material from the silo may be discharged through the outlet directly into a truck or other conveyance. As a specific example, storage silos are frequently used as surge containers for storing asphalt mix in the asphalt paving industry. Frequently, because of weather or other conditions, hot asphalt mix must be stored for later use. As a condition for storing the hot asphalt mix, the mix must be maintained at an elevated temperature in order to preclude the mix from setting up. Additionally, the mix must be stored in a sealed container to avoid oxidation which causes deterioration of the asphalt mix. One of the particular problems associated with storing hot asphalt mix is to provide an effective seal about the outlet opening of the silo.
One currently used seal for this purpose comprises a pair of concentric cylinders against which a gate is driven with a trolley system and wedges. The gate is closed about the silo outlet and grease is pumped into the annulus between the cylinders. While this system has worked satisfactorily, it is necessary for the gate to drive hard against the cylinders and to maintain the cavity between the cylinders clear so that the grease can fill the cavity. Unfortunately, debris becomes packed in this area, preventing the formation of a tight seal between the gate and the cylinders and oftentimes precluding the grease from filling the cavity to make the seal.
Other sealing systems for asphalt mixes are also known. For example, fluid seals, such as illustrated in U.S. Pat. Nos. 3,532,252 and 4,284,203 have been used. Also, an inflatable seal has been used, for example, as illustrated in U.S. Pat. No. 3,820,687. In that patent, the sliding action is strictly horizontal, causing the seal to abrade and generally wear.
According to the present invention, there is provided a gate and seal for a storage container which minimizes or eliminates the foregoing and other problems associated with the prior gates and seals for storage containers and provides a novel and improved gate and seal construction having various advantages in construction, mode of operation and use in comparison therewith. Particularly, the present invention includes a storage container, for example, a silo for containing hot asphalt mix having an outlet adjacent its lower end. The outlet is preferably in cylindrical form comprising the lower end of a frustoconical discharge chute. About the outside of the outlet is an annular chamber containing heating oil for maintaining the asphalt mix in the chute and outlet at an elevated temperature sufficient such that the material does not set up within the silo. Additionally, a second annular chamber is also disposed about the annular outlet opening and comprises an air chamber for feeding air to an underlying inflatable bladder. The bladder lies just above the plane containing the edge of the opening and, when inflated, may project below the edge.
The gate portion of the gate and seal combination of the present-invention includes a flat plate forming a gate for sealing against the cylindrical edge or margin of the outlet. The gate is mounted on a structural frame and has pairs of side rollers for rolling the frame and gate along a pair of spaced tracks forming part of the silo. The tracks are spaced relative to the margin of the outlet opening of the silo such that the gate may pass below the outlet margins in initial spaced relation thereto. The tracks have cam surfaces, e.g., wedges, which permit the frame and gate when the rollers engage along the inclined surfaces of the wedges to not only translate in a horizontal direction but also to move in a vertical direction. That is, the combination of the wedges and rollers permit the gate to move upwardly, i.e., in a direction opposite to the direction of the material flowing through the outlet when the gate lies in an open position. Because the gate engages the annular margin of the cylindrical opening, there is little danger of debris being caught between the gate and the annular margin. Also, the bladder does not engage the gate until the gate is seated against the cylindrical edge and movement of the gate has stopped. This precludes substantial wear and abrasion of the bladder. Further, because the bladder lies outside of the annular outlet and is inflatable, any debris caught on the plate below the bladder does not substantially affect the seal formed between the gate and the bladder. That is, the inflatable seal substantially seals about any such debris if it cannot seal directly against the top surface of the plate.
In a preferred embodiment according to the present invention, there is provided apparatus for selectively opening and closing a material flow outlet for a material storage container comprising means forming part of the storage container, including a peripheral margin defining the material flow outlet, a gate movable between open and closed positions respectively spaced from the outlet for opening the outlet and disposed about the margin for closing the outlet and an inflatable seal disposed about the peripheral margin of the outlet. Means are provided for inflating the seal for engagement with the gate about the peripheral margin of the outlet for substantially sealing the outlet when the gate lies in its closed position, the outlet enabling flow of material therethrough in a first direction when the gate is spaced from the outlet and in the gate open position. Also provided are means for mounting the gate for movement in a direction opposite the first direction and in a second direction generally normal to the first direction when the gate is moved from its open position into its closed position and means for moving the gate between the open and closed positions.
In a further preferred embodiment according to the present invention, there is provided apparatus for selectively opening and closing an outlet for discharging hot asphalt mix from a storage silo comprising means forming part of the storage silo including a peripheral margin defining the asphalt mix outlet, a gate movable between open and closed positions respectively spaced from the outlet for opening the outlet and disposed about the margin for closing the outlet and an inflatable seal disposed about the peripheral margin of the outlet. Means are provided for inflating the seal for engagement with the gate about the peripheral margin of the outlet for substantially sealing the outlet when the gate lies in its closed position, the outlet enabling flow of hot asphalt mix therethrough in a first direction when the gate is spaced from the outlet and in the gate open position. Means are disposed about the margin of the outlet for heating the hot asphalt mix within the outlet when the outlet is closed by the gate, with means for mounting the gate for movement in a direction opposite the first direction and in a second direction generally normal to the first direction when the gate is moved from its open position into its closed position and means for moving the gate between the open and closed positions.
Accordingly, it is a primary object of the present invention to provide a novel and improved gate and seal for a material storage container and particularly a gate and seal for a hot asphalt mix storage silo wherein the hot asphalt mix in the container is effectively sealed from oxidation.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.